Todd Young celebrates his win for the U.S. Senate seat as he addresses his supporters at the Indiana GOP election party Tuesday, November 8, 2016, at the at the JW Marriott.(Photo: Matt Kryger/IndyStar)Buy Photo

Congressman Todd Young pulled off a win Tuesday that months ago seemed politically improbable as the Republican defeated Evan Bayh for Indiana’s open U.S. Senate seat.

Young, a Bloomington Republican, was outfunded and not as well-known as Bayh, a former two-term U.S. senator and Indiana governor. But throughout the campaign, Young put Bayh on the defensive as the Democrat struggled to address questions over his Indiana residency and whether he used his standing as a senator to fuel a lucrative career after he originally left office in 2011.

For Young, his win over Bayh could have national implications. Republicans viewed the race as key in determining control of the Senate.

With 51 percent of precincts reporting, Young led Bayh 53 percent to 41 percent.

"Just a few minutes ago, I had the opportunity to speak with Senator Bayh," Young said during his victory speech.

Someone in the audience yelled loudly, "Bye, Bayh."

"No, no," Young said. "I thanked him for his commitment to public service and the contributions he and his family have made over the years, all in the name of making Indiana and our nation a better place."

He then asked for, and received, applause for the Bayh family.

"Our Democrat neighbors fought hard. But now it's time to come together for the good of our state and country," Young said. "Our challenges and our enemies don't know us as Republicans or Democrats, only Hoosiers and Americans. We must face our challenges as Hoosiers and Americans."

For Bayh, the defeat is a significant blow to his legacy after he shocked the political world by entering the race in July and attempting a comeback. He saw his wide lead in the polls dissipate as Young gained ground, helped by outside groups.

With Bayh increasingly vulnerable, outside groups poured more than $44 million into the race since July, with Young receiving a higher portion of the cash. In the waning days of the campaign, political rating agencies predicted an upset, shifting the race to “toss up” — or tilting the outcome in Young’s favor.

In addressing his defeat, Bayh said "despite what some people may tell you, we have more in common than divides us."

He then told the crowd that Election Day was the 21st birthday of his sons Nick and Beau. The crowd sang "Happy Birthday" to the college students, who became instant Hoosier celebrities when they were born while Bayh was governor.

As the campaign heated up, Young forced Bayh on the defensive, attacking him as a Washington insider who had left the Hoosier state for high-paying jobs, including at private equity giant Apollo Global Management. He also railed on Bayh’s support of Obamacare, though Bayh said he would support changes to make the law better for small businesses.

Meanwhile, Bayh criticized Young for his support of free trade policies, a controversial issue in manufacturing-heavy Indiana, where companies have announced plans to offshore jobs. Young pivoted to define himself as a supporter of “fair trade” in the wake of decisions by air conditioner manufacturer Carrier and an affiliate to lay off 2,100 Hoosier workers and move production to Mexico. Bayh also sought to paint Young as a tea party activist who opposed the auto industry bailout that Bayh argued saved Hoosier jobs.

In appealing to voters, Bayh maintained that he has “always voted for the best interest of Hoosiers. Without exception.”

Young has pledged to stand up “to the Washington insiders in both parties.”

Those assertions came amid concerns that Young’s reliance on funding from outside groups, such as the Senate Leadership Fund, a super PAC with ties to Senate Majority Leader Mitch McConnell, would make him beholden to their causes.

For Bayh, his campaign was forced to be less about what he planned to accomplish in the Senate and more about responding to a series of reports about his conduct in office.

Bayh was hurt by news reports revealing parts of his private Senate schedule, showing he met in 2010 with Apollo officials while still dealing with issues affecting the financial industry, despite his campaign telling IndyStar he had not.

Just last week, Bayh’s campaign announced he would repay taxpayers for expenses related to five overnight hotel stays in Indianapolis during his time in the Senate. He stayed in a hotel even though he could have stayed in his modest Indianapolis condo. Campaign officials acknowledged that reimbursements the former senator received for those nights in 2009 were prohibited by Senate rules. Bayh said he would personally repay $737.

Bayh, who saw his wealth soar after leaving the Senate, also sought to address questions over his financial interests. Bayh and his wife, Susan, own assets worth between $13.7 million and $47.7 million, according to a recent federal financial disclosure.

“Six years ago, I left Congress fed up with the partisanship,” Bayh said in an ad released this month. “Yes, I built a good life for my family, spent time with Susan and our boys. … The corrupt interests now falsely attacking me, they’re the same ones hurting you.”

Young’s campaign also had its share of controversies, including the resurfacing of issues surrounding unpaid property taxes. CNN found that Young, in 2012, improperly claimed a house he wasn’t living in as his primary residence. That allowed him to wrongly receive a $5,000 tax break on the house. His campaign said once Young learned of the error, he paid what he owed.

And in the primary, Young had to fight off a challenge to his candidacy led by Indiana Democrats and his Republican primary opponent, U.S. Rep. Marlin Stutzman. They had accused him of not having enough signatures from Hoosier voters to run for U.S. Senate, a charge the campaign denied.

Young surfaced from the primary victorious — and with a win in November all but assured.

Until Bayh got in.

Then Young became the underdog, attempting to defeat a storied politician. And he somehow managed to do it.

Auditor Suzanne Crouch, Republican candidate for Lieutenant Governor of Indiana, greets the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for lieutenant governor, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Lt. Gov. Eric Holcomb, the Republican candidate for Indiana governor, prepares to speak to the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for governor, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Auditor Suzanne Crouch, Republican candidate for Lieutenant Governor of Indiana, and Lt. Gov. Eric Holcomb, the Republican candidate for Indiana governor, greet the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for governor, Tuesday, November 8, 2016. Jenna Watson/IndyStar

The crow reacts as Rep. Todd Young, the Republican candidate for U.S. Senate, and his family take the stage for Young to speak at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for Senate, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Rep. Todd Young, the Republican candidate for U.S. Senate, and his family take the stage for Young to speak to the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for Senate, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Rep. Todd Young, the Republican candidate for U.S. Senate, speaks to the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for Senate, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Jenny Young listens as her husband, Rep. Todd Young, the Republican candidate for U.S. Senate, speak to the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for Senate, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Newly elected Indiana Attorney General Curtis Hill and former attorney general Greg Zoeller,right, celebrate with his supporters at the Indiana GOP election party Tuesday, November 8, 2016, at the at the JW Marriott. Matt Kryger/IndyStar

Kent Morgan reacts to an early presidential projection showing Trump in lead, during the Indiana Republican watch party at the J.W. Marriott, Indianapolis, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Members of the Indiana Republican party watch the election results slowly come in on FOX New at the Indiana GOP election party Tuesday, November 8, 2016, at the at the JW Marriott. Matt Kryger/IndyStar

Indiana Speaker of the House Brian Bosma talks with members of the Indiana Republican party as they waits for election results at the Indiana GOP election party Tuesday, November 8, 2016, at the at the JW Marriott. Matt Kryger/IndyStar

Lt. Gov. Eric Holcomb, the Republican candidate for Indiana governor, speaks to the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for governor, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Auditor Suzanne Crouch, Republican candidate for Lieutenant Governor of Indiana, and Lt. Gov. Eric Holcomb, the Republican candidate for Indiana governor, greet the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for governor, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Auditor Suzanne Crouch, Republican candidate for Lieutenant Governor of Indiana, greets the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for lieutenant governor, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Lt. Gov. Eric Holcomb, the Republican candidate for Indiana governor, speaks to the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for governor, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Janet Holcomb greets the crowd before her husband, Lt. Gov. Eric Holcomb, the Republican candidate for Indiana governor, speaks to the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for governor, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Auditor Suzanne Crouch, Republican candidate for Lieutenant Governor of Indiana, speaks to the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for lieutenant governor, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Rep. Todd Rokita speaks to the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the spot as U.S. Representative for IndianaÕs 4th district, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Members of the Indiana GOP react to Eric Holcomb's win as Indiana's next governor during the Indiana Republican watch party at the J.W. Marriott, Indianapolis, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Rep. Todd Young, the Republican candidate for U.S. Senate, speaks to the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for Senate, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Members of his family stand near as Rep. Todd Young, the Republican candidate for U.S. Senate, speaks to the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for Senate, Tuesday, November 8, 2016. Jenna Watson/IndyStar

His parents stand near as Rep. Todd Young, the Republican candidate for U.S. Senate, speaks to the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for Senate, Tuesday, November 8, 2016. Jenna Watson/IndyStar

His children stand near as Rep. Todd Young, the Republican candidate for U.S. Senate, speaks to the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race for Senate, Tuesday, November 8, 2016. Jenna Watson/IndyStar

Prosecutor Curtis Hill, the Republican candidate for Indiana's attorney general, speaks to the crowd at the Indiana GOP watch party at the J.W. Marriott in Indianapolis, after winning the race, Tuesday, November 8, 2016. Jenna Watson/IndyStar